Device for producing cold at low temperatures

ABSTRACT

A cold gas refrigerator operable with an expansion device where a fluid medium is further expanded and cooled, and a compressor to raise the pressure of said further expanded medium, the compressor formed of a compression chamber within the axially movable displacer of the refrigerator and a piston fixed to the refrigerator housing and extending into the chamber.

Umted States Patent 1151 3,638,441 Rietdiik Feb. 1, 1972 [541 DEVICE FOR PRODUCHNG cow AT [56] References cm R LOW TEMPERATU Es UNITED STATES PATENTS 72 I t h Ad Ri td"k, E dh I 1 fi fifl f e u m 3,101,596 8/1963 Rinia ..62/6 3,327,486 6/1967 Kohler ..62/6 [73] Asslgneez U.S. Phlllps Corporatwn, New York, NY. 7 [22] Filed: Mar. 3, 1970 Primary Examiner-William J. Wye [21] APPL NOJ 16 150 Attorney--Frank R. Trifari ABSTRACT [30] Forelgn Apphcauon Pnonty Data A cold gas refrigerator operable with an expansion device Mar. 6, 1969 Netherlands ..69/03436 where a fluid medium is further expanded and cooled, and a [52] Us CL H 62/6 compressor to raise the pressure of said further expanded [51] medium, the compressor fonned of a compression chamber 58 Field ofSeareh ..62/6 Within the axially movable displacer of the refrigerator and a piston fixed to the refrigerator housing and extending into the chamber.

PATENTED FEB 1 I872 SHEU 2 BF 2 JNVENTOR.

JOHAN ARIETDUK DEVICE FOR PRODUCING COLD AT LOW TEMPERATURES The invention relates to a device for producing cold at low temperature, which comprises at least one cold-gas refrigerator having at least one compression space of a variable volume and a higher average temperature, as well as at least two expansion spaces of likewise variable volume and lower average temperature than that of the compression space, said spaces communicating with each other; a regenerator is present in each of the communications, with the volume of the said expansion spaces being variable by a pistonlike body which is composed of parts having different diameters. An outlet valve is arranged in the wall of the final expansion space having the lowest average temperature during operation, said valve opening when the pressure in said space is higher than the minimum pressure and preferably is substantially equal to the maximum pressure which occurs in the cold-gas refrigerator. A duct communicates with this valve which duct communicates, via the high-pressure side of one or several heat exchangers, with an expansion device in which the working medium expands; this medium is then in the heat exchange relationship with a place to be cooled, from which space the working medium flows back, viathe low-pressure side of the heat exchangers and a compression device, to an inlet valve which communicates with one of said spaces of the cold-gas refrigerator.

Devices of the above-described type are known. The working medium exhausted from the expansion space having the lowest temperature is reduced in pressure, after having passed the said heat exchangers, in a Joule-Kelvin valve, a throttle ejector or other expansion device. In order to achieve a proper cold production or low temperature it is necessary to expand to pressures below the minimum pressure which occurs in the cold-gas refrigerator. This means that the expanded working medium, before its return to the cold-gas refrigerator, has to be compressed by means of a compressor to at least the said minimum pressure of the cold-gas refrigerator. In order to minimize the losses, the compressor operates at room temperature. This means that heat exchangers will have to be present between the compressor and the part of the device which has a low temperature. The extra compressor and the required heat exchangers make the known device complicated and expensive.

it is the object of the invention to provide a device of the above-described type having a simple compact construction and in which the number of required heat exchangers is strongly reduced as compared with known devices.

The device according to the invention is characterized in that the compression device is formed by a cylinder incorporated in the piston which is capable of varying the volume of the expansion spaces; in this cylinder a hollow further piston rigidly secured to the wall of one of the expansion spaces, can move in such manner that the centerlines of the cylinder and the further piston coincide with or are parallel to the centerline of the relative piston; the further piston communicates on its side connected to the wall, with the duct through which low-pressure working medium can flow from the expansion device to the cold-gas refrigerator, and comprises on its other side a suction valve through which working medium can flow into the cylinder. The side of the cylinder facing the interior of the piston is closed by a plate in which a pressure valve is provided which opens when the pressure in the cylinder is higher than the minimum, pressure which occurs in the said expansion and compression space. This compression valve forms a communication between the space in the cylinder and a buffer space likewise present in the cylinder, said buffer space communicating, via a nonreturn valve, with an expansion space having a higher average temperature than the expansion space having the lowest average temperature during operation; the nonreturn valve can open in the direction of the said expansion space.

In the device according to the invention, the compressor is thus constructed as a part of the cold-gas refrigerator, so that the same can operate very easily at low temperatures. Since consequently no heat exchangers are required any longer between the compressor operating at room temperature and the cold-gas refrigerator, an important simplification has been obtained. Since the compressor is accommodated in the coldgas refrigerator, no extra sealing problems to the outside present themselves.

In order that the invention may be readily carried into effect, two embodiments of devices for producing cold will now be described in greater detail, by way of example, with reference to the accompanying diagrammatic drawings, which are not drawn to scale.

FIG. 1 is a sectional view of one embodiment of the invention.

FIG. 2 is a sectional view of another embodiment of the invention.

Referring now to FIG. 1, reference numeral 1 denotes a cylinder. This cylinder comprises a piston 2 and a displacer which consists of two parts or portions 3 and 4. The piston and the displacer are connected, by means of a piston rod 5 and a displacer rod 6, to a driving mechanism not shown. A compression space 7 is present between the piston 2 and the part 3 of the displacer. The compression space 7 communicates with an intermediate expansion space 11 via a cooler 8, a regenerator 9 and a freezer 10. The volume of the intermediate expansion space 11 is varied during operation by the annular surface 12 which is formed as a result of the difference in diameter between the parts 3 and 4 of the displacer. The intermediate expansion space 11 communicates, via a regenerator l3 and a freezer 14, with the final expansion space 15. Via a springloaded outlet valve 16, the final expansion space 15 communicates with a duct 17 which communicates with a throttle valve 19 via heat exchanger 18. The pressure at which medium is admitted from the expansion space 15 to the system of ducts can be adjusted by suitable choice of the outlet valve 16. After the expansion of the medium in the throttle valve 19, it is conveyed along a place 20 to be cooled, after which the pressure-reduced medium flows back to the cold-gas refrigerator via heat exchanger 18.

Since now the pressure of the medium will be lower than the minimum pressure which occurs in the cold-gas refrigerator, this medium should thus be compressed to approximately said minimum pressure. For that purpose the following arrangement is made. A cylinder 21 is accommodated in the displacer. In this cylinder is accommodated a piston 22 which is hollow, and the upper side of which is secured to the wall of the expansion space 15. On its lower side this body is closed and comprises a suction valve 23. At the area 29 the interior of the piston is in open communication with the duct 25 communicating with the throttle valve. The cylinder 21 is closed on its lower side by a plate 26 in which a compression valve 27 is accommodated. Via said valve 27 the space 28 in the cylinder 21 can be made to communicate with a buffer space 29. The buffer space 29 communicates, via a duct 30 and a nonreturn valve 31, with the intermediate expansion space 11.

The operation of the cold-gas refrigerator is assumed to be known. Furthermore the operation is as follows: when the pressure in the refrigerator has reached a given value, the outlet valve 16 opens and working medium flows into the duct 17. This medium passes the heat exchanger 18 and then expands in the throttle valve 19 to a pressure which is lower than the minimum pressure which occurs in the cold-gas refrigerator. The expanded very cold medium is then conducted along the place 20 to be cooled where it volatilizes again. When the pressure in the space 28 in the cylinder 21 is lower than the pressure in the duct 25 in which expanded medium is present, the valve 23 opens and said expanded medium is sucked into space 28. When the pressure begins to rise again, the valve 23 closes. When the pressure in the space 28 is equal to the minimum pressure which occurs in the cold-gas refrigerator, the compression valve 27 opens and medium flows in the buffer space 29. So medium is present in the buffer space under a pressure which is equal to the minimum pressure of the refrigerator. When the pressure in the refrigerator drops, as a result of the exhaust of medium, to slightly below said pressure, the nonreturn valve 31 opens and medium flows from the buffer space into the intermediate expansion space 31. The compression in the space 28 occurs adiabatically so that the working medium will be heated to approximately the temperature of the intermediate expansion space 11, after which the compressed medium is supplied to said space.

in this manner a device is obtained with which cold can be produced at very low temperatures without this requiring an extra compressor operating at room temperature and many extra heat exchangers. Since the compression in the device according to the invention occurs entirely in the cold-gas refrigerator, no extra sealing problems present themselves either in this device. Although in the example the expansion takes place in a throttle valve, it will be obvious that this can take place also, if desirable, in another expansion device, for example, a throttle ejector, a piston expansion machine or an expansion turbine.

FIG. 2 shows a device which in general corresponds to the device shown in FIG. 1. In this figure the cold-gas refrigerator is constructed as a refrigerator having three expansion spaces, namely the final expansion space and the two intermediate expansion spaces 11 and 51. Those components which correspond to those of FIG. 1 are referred to by the same reference numerals. The displacer is constructed from three parts 3, 52 and 4 having different diameters in which the annular surfaces 12 and 53 vary the volume of the intermediate expansion spaces 11 and 51. The regenerator 54 and the freezer 55 are accommodated between said expansion spaces. The further piston is constructed from two parts 22 and 56 of different diameters. The annular surface 57 varies the volume of a first compression space 58 which communicates, via an inlet valve 23, with the interior of the piston part 22. The end face of the piston part 56 varies the volume of the compression space 28 which communicates, via the outlet valve 27, with the buffer space 29 which opens into the intermediate expansion space 11, via the duct 30 and nonreturn valve 31 incorporated therein, which expansion space is situated nearest to the compression space 7. The compression spaces 58 and 29 are arranged in series by a duct 59 having incorporated therein a buffer space 60. The duct 59 is in heat exchange relationship with the freezer 55 at the area 61.

In this device, medium which is expanded in the valve 19, is first compressed in the compression space 58, then intermediately cooled at the area 61 to approximately the temperature of the intermediate expansion space 51, and then further compressed in the expansion space 28 to substantially the minimum pressure which occurs in the working space of the refrigerator. This medium in the expansion space 11 is then supplied to the refrigerator. it will be obvious that if the refrigerator comprises more intermediate expansion spaces, the compressor can also be extended. in this manner an extremely reliable and readily operating device for producing cold at low temperatures has been obtained.

What is claimed is:

l. A device for producing cold at low temperatures comprising at least one cold-gas refrigerator having at least one compression space of a variable volume and a higher average temperature, as well as at least two expansion spaces of likewise variable volume and lower average temperature than that of the compression space, said spaces communicating with each other and a regenerator being present in each of the communications, the volume of the said expansion spaces being variable by a pistonlike body which is constructed from parts having different diameters, an outlet valve being arranged in the wall of the final expansion space having the lowest average temperature during operation, said valve opening when the pressure in said space is higher than the minimum pressure and preferably is substantially equal to the maximum pressure which occurs in the cold-gas refrigerator, a duct communicating with said valve which duct communicates via the high-pressure side of one or more heat exchangers with an expansion device in which the working medium expands, said medium being in heat exchange relationship with a place to be cooled, from which place the working medium flows back, via the low-pressure side of the said heat exchangers and a compression device to an inlet valve which communicates with one of the said spaces of the cold-gas refrigerator, characterized in that the compression device is formed by a cylinder incorporated in the pistonlike body which can vary the volume of the expansion spaces, in which cylinder a hollow further pistonlike body which is rigidly secured to the wall of one of the expansion spaces and move in such manner that the centerline of the cylinder-piston combination coincides with or is parallel to the centerline of the relative pistonlike body, the further pistonlike body communicating, on its side connected to the wall, with the duct through which low-pressure medium flows from the expansion device to the cold-gas refrigerator and comprising on its other side a suction valve through which working medium can flow into the cylinder, the cylinder on its side facing the interior of the pistonlike body being closed by a plate in which a pressure valve is provided which opens when the pressure in the cylinder exceeds the minimum pressure which occurs in the said expansion and compression spaces, said valve opening into a buffer space which, via a nonreturn valve, communicates with an intermediate expansion space having a higher average temperature than that prevailing in the final expansion space, said nonreturn valve opening in the direction of said intermediate expansion space.

2. A device as claimed in claim 1, characterized in that the cold-gas refrigerator comprises more than two expansion spaces and the further pistonlike body is constructed from a number of parts which, viewed from the connection of said body to the wall of the cold-gas refrigerator, show a decreasing diameter and in which each of the annular surfaces constituted by the transition of two adjacent parts influence the volume of a compression space, the various compression spaces being arranged in series through ducts having incorporated therein buffer spaces, if desirable, the inlet of the first compression space communicating with the low-pressure side of the said heat exchanger and the outlet of the last compression space communicating, via an outlet valve and a buffer space, if desirable, with an inlet valve which opens into the intermediate expansion space which is situated nearest to the compression space, each of the ducts between two successive compression spaces being in heat exchange relationship with the medium in an associated intermediate expansion space.

3. In a cold-gas refrigerating apparatus, including a displacer movable within a housing and defining therein at least one variable-volume expansion space in which working medium is expanded to a first pressure and temperaturc, this apparatus operable with a further expansion device wherein the medium is further expanded to a second temperature and pressure lower than said first temperature and pressure, the improvement in combination therewith of means for compressing said further expanded medium comprising a compression chamber defined as a bore within said displacer, a piston fixed to said housing and extending into said chamber which chamber moves relative to the piston when the displacer moves, first duct means communicating the further expanded medium from the further expansion device into said compression space, and second duct means communicating the medium from the compression chamber to one of said expansion spaces.

4. Apparatus according to claim 3 further comprising a oneway outlet valve for permitting medium flow from said expansion space to said further expansion device, a one-way suction valve for permitting medium flow from said further expansion device to said compression chamber, and another one-way valve for permitting medium flow from the compression chamber to said expansion space.

5. Apparatus according to claim 3 wherein said compression chamber comprises a first part into which said piston extends, and a second part buffer space, and a one-way valve permitting medium flow from said first to said second part of said chamber.

6. Apparatus according to claim 4 wherein said compression chamber comprises a first part into which said piston extends, and a second part buffer space, and a one-way valve permitting medium flow from said first to said second part of said chamber.

7. in a cold-gas refrigerating apparatus, including a displacer movable within a housing and defining therein at least one variable-volume expansion space in which working medium is expanded to a first pressure and temperature, this apparatus operable with a further expansion device wherein the medium is further expanded to temperature and pressure lower than said first temperature and pressure, the improvement in combination therewith of means for compressing said further expanded medium to be returned to said expansion space for recycling, comprising a compression chamber formed as a bore within said displacer, the bore defining a compression space and a buffer space, and a one-way valve which separates and permits flow only from the compression space into the buffer space, a duct communicating the buffer space to said expansion space with a one-way valve therebetween permitting flow only from the buffer space into the expansion space, a hollow piston secured to the housing and extending into said compression space for compressing medium therein when the displacer moves relative to the fixed piston, a one-way valve in said piston for permitting flow of further expanded medium only from the expansion device through the piston into the compression space.

8. Apparatus according to claim 5 having at least two expansion spaces one of higher temperature and pressure than the other, and wherein said compression chambers first part and second buffer part define a first portion, and the chamber comprises a second portion similar to and axially spaced from the first portion, said piston has two portions corresponding to the first and second portions of the compression chamber, and the buffer space of said second portion communicates with said expansion space of higher temperature and pressure.

9. Apparatus according to claim 8 further comprising heat exchange means between the first compression chamber and an expansion space having lower temperature than said first compression space. 

1. A device for producing cold at low temperatures comprising at least one cold-gas refrigerator having at least one compression space of a variable volume and a higher average temperature, as well as at least two expansion spaces of likewise variable volume and lower average temperature than that of the compression space, said spaces communicating with each other and a regenerator being present in each of the communications, the volume of the said expansion spaces being variable by a pistonlike body which is constructed from parts having different diameters, an outlet valve being arranged in the wall of the final expansion space having the lowest average temperature during operation, said valve opening when the pressure in said space is higher than the minimum pressure and preferably is substantially equal to the maximum pressure which occurs in the cold-gas refrigerator, a duct communicating with said valve which duct communicates via the high-pressure side of one or more heat exchangers with an expansion device in which the working medium expands, said medium being in heat exchange relationship with a place to be cooled, from which place the working medium flows back, via the lowpressure side of the said heat exchangers and a compression device to an inlet valve which communicates with one of the said spaces of the cold-gas refrigerator, characterized in that the compression device is formed by a cylinder incorporated in the pistonlike body which can vary the volume of the expansion spaces, in which cylinder a hollow further pistonlike body which is rigidly secured to the wall of one of the expansion spaces and move in such manner that the centerline of the cylinder-piston combination coincides with or is parallel to the centerline of the relative pistonlike body, the further pistonlike body communicating, on its side connected to the wall, with the duct through which low-pressure medium flows from the expansion device to the cold-gas refrigerator and comprising on its other side a suction valve through which working medium can flow into the cylinder, the cylinder on its side facing the interior of the pistonlike body being closed by a plate in which a pressure valve is provided which opens when the pressure in the cylinder exceeds the minimum pressure which occurs in the said expansion and compression spaces, said valve opening into a buffer space which, via a nonreturn valve, communicates with an intermediate expansion space having a higher average temperature than that prevailing in the final expansion space, said nonreturn valve opening in the direction of said intermediate expansion space.
 2. A device as claimed in claim 1, characterized in that the cold-gas refrigerator comprises more than two expansion spaces and the further pistonlike body is constructed from a number of parts which, viewed from the connection of said body to the wall of the cold-gas refrigerator, show a decreasing diameter and in which each of the annular surfaces constituted by the transition of two adjacent parts influence the volume of a compression space, the various compression spaces being arranged in series through ducts having incorporated therein buffer spaces, if desirable, the inlet of the first compression space communicating with the low-pressure side of the said heat exchanger and the outlet of the last compression space communicating, via an outlet valve and a buffer space, if desirable, with an inlet valve which opens into the intermediate expansion space which is situated nearest to the compression space, each of the ducts between two successive compression spaces being in heat exchange relationshIp with the medium in an associated intermediate expansion space.
 3. In a cold-gas refrigerating apparatus, including a displacer movable within a housing and defining therein at least one variable-volume expansion space in which working medium is expanded to a first pressure and temperature, this apparatus operable with a further expansion device wherein the medium is further expanded to a second temperature and pressure lower than said first temperature and pressure, the improvement in combination therewith of means for compressing said further expanded medium comprising a compression chamber defined as a bore within said displacer, a piston fixed to said housing and extending into said chamber which chamber moves relative to the piston when the displacer moves, first duct means communicating the further expanded medium from the further expansion device into said compression space, and second duct means communicating the medium from the compression chamber to one of said expansion spaces.
 4. Apparatus according to claim 3 further comprising a one-way outlet valve for permitting medium flow from said expansion space to said further expansion device, a one-way suction valve for permitting medium flow from said further expansion device to said compression chamber, and another one-way valve for permitting medium flow from the compression chamber to said expansion space.
 5. Apparatus according to claim 3 wherein said compression chamber comprises a first part into which said piston extends, and a second part buffer space, and a one-way valve permitting medium flow from said first to said second part of said chamber.
 6. Apparatus according to claim 4 wherein said compression chamber comprises a first part into which said piston extends, and a second part buffer space, and a one-way valve permitting medium flow from said first to said second part of said chamber.
 7. In a cold-gas refrigerating apparatus, including a displacer movable within a housing and defining therein at least one variable-volume expansion space in which working medium is expanded to a first pressure and temperature, this apparatus operable with a further expansion device wherein the medium is further expanded to temperature and pressure lower than said first temperature and pressure, the improvement in combination therewith of means for compressing said further expanded medium to be returned to said expansion space for recycling, comprising a compression chamber formed as a bore within said displacer, the bore defining a compression space and a buffer space, and a one-way valve which separates and permits flow only from the compression space into the buffer space, a duct communicating the buffer space to said expansion space with a one-way valve therebetween permitting flow only from the buffer space into the expansion space, a hollow piston secured to the housing and extending into said compression space for compressing medium therein when the displacer moves relative to the fixed piston, a one-way valve in said piston for permitting flow of further expanded medium only from the expansion device through the piston into the compression space.
 8. Apparatus according to claim 5 having at least two expansion spaces one of higher temperature and pressure than the other, and wherein said compression chamber''s first part and second buffer part define a first portion, and the chamber comprises a second portion similar to and axially spaced from the first portion, said piston has two portions corresponding to the first and second portions of the compression chamber, and the buffer space of said second portion communicates with said expansion space of higher temperature and pressure.
 9. Apparatus according to claim 8 further comprising heat exchange means between the first compression chamber and an expansion space having lower temperature than said first compression space. 